The hits just keep on coming… The referendum debate has produced its first resignation threat. Stewart Jackson, Parliamentary Private Secretary to the Northern Ireland Secretary, Owen Patterson, says he will vote for the motion even if it costs him his job. The rumour mill suggests at least one other PPS has been hauled before the chief whip today. Now, the departure of a PPS, a "parliamentary aide" or "bag carrier", is hardly a death blow, but it does represent visible dissent from the government line, and resignations by actual ministers would certainly hurt.

Meanwhile, the debate itself been switched to next Monday - to enable William Hague to lead for the government and David Cameron to attend, Downing Street says. It looks as if all parties are planning to whip their MPs against the motion (at the time of writing, and things are shifting with some speed at the moment).

Will the visible presence of their leaders bring Tory dissidents into line? It might swing some MPs, particularly the phalanx of newcomers whose instinctive Euroscepticism wars with their equally instinctive loyalty to the leader who got them elected. Many of these resent whipping decisions which put them between a rock and a hard place, and wish the government had shrugged, noted that the motion would not have been binding and downplayed the whole thing... And when asked how they plan to vote, they start muttering about how difficult it all is.

The Eurosceptic camp is keeping up the momentum by adding new signatures to the David Nuttall motion today. The total of Conservative MPs signing has passed 60 on today's order paper. And there are some interesting new names, notably John Whittingdale, the respected chair of the Culture Media and Sport Committee and several prominent new intake MPs. (Mr Jackson can presumably be added to the list as well.)

Some MPs are complaining about the parties applying the whip in a backbench debate - although on an issue of this magnitude it doesn't seem to be entirely unreasonable. But it may prove counter-productive. In this Parliament MPs have been much more rebellious and much more inclined to vote according to conscience, and plenty are more inclined to tell their whips how they are voting, rather than be told how they should vote.